First time I saw this was when my school did it as a school opera.  The libretto does not actually specify forty street urchins singing treble for the Act 1 finale, but that's what happened.  Rosina and Berta were bussed in (and Berta got her aria) but the male principals were all sung by 17/18 year old boys.

I can still remember the stage presence of the boys singing Bartolo and Basilio during their arias.  That says something about the acting ability, maybe something about the power of live performance, which after years of experience you lose.

I still think Il barbiere is a hard hearted work, if fun.  Rosina reminds me of a P G Wodehouse heroine.  I can imagine here saying "You mean you wouldn't do a little thing like pinch a policeman's helmet for me?"

This is an old trick for amateur productions. All those little urchins bring their parents, grandparents, brothers and sisters and the tickets sell much more easily. I played in the band in adult, amateur productions of Oklahoma and The King and I and they had plenty of schoolchildren. (The King and I has a few anyway but this production had many more than just the king's offspring.)